A199305 Palindromic primes in the sense of A007500 with digits '0', '1' and '5' only.

5, 11, 101, 151, 1151, 1511, 10151, 10501, 11551, 15101, 15511, 15551, 100511, 110051, 115001, 150011, 150151, 151051, 1001551, 1051051, 1055501, 1115551, 1150151, 1150511, 1501501, 1510511, 1550551, 1551001, 1551551, 1555111, 10000511, 10011101, 10011511, 10055011, 10101551

Offset

1,1

Comments

All terms, except for the initial 5, start and end with the digit '1'. This fact could be used to significantly speed up the given program.

Links

Table of n, a(n) for n=1..35.

Prog

(PARI) a(n=50, list=0, L=[0, 1, 5], needpal=1)={ for(d=1, 1e9, u=vector(d, i, 10^(d-i))~; forvec(v=vector(d, i, [1+(i==1&!L[1]), #L]), isprime(t=vector(d, i, L[v[i]])*u) || next; needpal & !isprime(A004086(t)) & next; list & print1(t", "); n-- || return(t)))}  \\ M. F. Hasler, Nov 06 2011
(Magma) [p: p in PrimesUpTo(10^8) | Set(Intseq(p)) subset [0, 1, 5] and IsPrime(Seqint(Reverse(Intseq(p))))]; // Bruno Berselli, Nov 07 2011

Crossrefs

Cf. A020449-A020472, A199325-A199329, A087510-A087515.

Sequence in context: A030079 A066596 A199325 * A096473 A007530 A157967

Adjacent sequences: A199302 A199303 A199304 * A199306 A199307 A199308

Keyword

nonn,base

Author

M. F. Hasler, Nov 06 2011

Status

approved